A Report of Contemporary Rammed. North America

Transcription

1 A Report of Contemporary Rammed Earth Construction and Research in North America ISISS 2011 & US Workshop on Earth Based Materials and Sustainable Structures Oct 28 30, 2011, Xiamen, China Bly Windstorm

2 Historic Rammed Earth Nepal Modern Rammed Earth North America 2

3 Yuchanglou Yongding, Fujian Plum Creek Pumping Station British Columbia, Canada n Yuchanglou.JPG Yuchanglou 3

4 Insulation & Steel XPS Foam Insulation Rock Wool Insulation 4

5 Masonry & Concrete Analogy 5

6 Unusually Challenging Site 6

7 Rammed Earth Compressive Strength 7

8 Steel Specifications & Concrete Code 8

9 Steel Placement Protocol 9

10 10

11 Typical Steel Placement at Wall Cap 11

12 Balance 12

13 Embodied Energy Comparison B.V. Venkatarama Reddy, P. Prasanna Kumar from the Department of Civil Engineering, Indian Institute of Science Embodied energy in CSRE walls (with 8% cement) is only about 15 25% of the embodied energy in burnt clay brick masonry CSRE with 8% cement gives 17% higher compressive strength when compared to brick masonry strength Compressive Strength of 338MPa with hand Compressive Strength of 3.38 MPa with hand rammers (20% of what is typical with pneumatics) 13

14 Embodied Energy in Structures 14

15 Thermal Performance (R=26) 15

16 M. A. Hall Assessing the moisture content dependent it t t d tparameters of stabilized earth materials using the cyclic response admittance method,

17 Stuart Fix & Russell Richman Viability of Rammed Earth Building Construction in Cold Climates, 2009 Insulated rammed earth walls achieve high levels of thermal resistance [and] can actually improve the thermal mass performance over solid rammed earth construction a composite rammed earth envelope is highly applicable in all climate zones 17

18 Insulation and Through Ties 18

19 Compaction Forces 19

20 20

21 Stabilized Rammed dearth hresearch The North American Rammed Earth Builders Association (NAREBA) Thor A. Tandy, P. Eng, C. Eng, Struct. Eng, MIStructE, of Unisol Engineering British Columbia Institute of Technology (BCIT) Funding from the Cement Assoc. of Canada 21

22 Compression Testing of The Soil 22

23 Vertical Rebar Pull Out 23

24 Horizontal Rebar Pullout 24

25 Flexural Beam Tests 25

26 Out Of Plane Bending of Composite Columns 26

27 Tests were designed to simulate the methods of construction typical to stabilized rammed earth structures Sample size is small and results must be viewed din that t context t 27

28 The Mix DrumStyle Mixer Stabilized Earth Mix 28

29 Compression Strength Comparison 6 PVC Rammed Cylinder Composite Wall Simulation for Cores 29

30 Compression Strength Comparison PVC Cast Cylinders Cored Cylinders 30

31 Shear Profiles 31

32 Compression Test Results PVC Cast Cylinders Average strength at 6 days 12 MPa (1741 psi) Average strength at 12 days 16MPa (2221psi) Cored Cylinders Average strength at 16 days 15 MPa (2176 psi) 32

33 Vertical Rebar Pull Out Tests (VPO) Marked Specimen Specimen in Baldwin Machine 33

34 Vertical Rebar Pull Out Tests (VPO) Specimen Fracture Bar Yield 34

35 VPO Results 10M (#3) Phase 1 10M (#3) VPO Two specimens tested Specimens had a high degree of variability Specimen A Yield in excess of 3 MPa Specimen B Pull out in excess of 1.5 Mpa 35

36 15M (#4) Results Phase 1 & Phase 2 15M (#4) VPO Phase 1 Two specimens tested Specimens in Phase 1 damaged in handling Unable to provide useful data 15M (#4) VPO Phase 2 Two Specimens tested Specimens provided consistent results Yield reached hdwith iha bond strength 29MP 2.9MPa (420 psi) 36

37 VPO Results 20M (#5) Phase 1 & Phase 2 Two specimens tested 20M (#5) VPO Phase 1 Yield reached on both with a bond strength in excess of 5 MPa (725 psi) 20M (#5) VPO Phase 2 Two Specimens tested Pull out achieved ed in excess ecessof 4 MPa (600psi) 37

38 VPO & HPO Results (Phase 1) 38

39 Horizontal Bar Pull Out (HPO) Typical Specimen Specimen In Baldwin Machine 39

40 Horizontal Bar Pull Out (HPO) Bar Yield 40

41 Horizontal Bar Pull Out Results 10M (#3) rebars Two specimens tested Results were consistent with one specimen reaching yield and one pulling out after reaching a bond strength of slightly less than 2.5 MPa (363 psi) 41

42 Thor Tandy (Unisol Engineering) Engineering Conclusions, R&D #1, BCIT Results suggest the ramming procedure has a direct effect on the bond stress. There may be a mechanical connection between the steel and SRE that is unlike the cement bond that occurs in concrete or masonry models, and this would likely be affected by the thoroughness of the compaction. The test results outperformed the equivalent in concrete or masonry by a significant factor There was no significant difference of bond stress with the various bar diameters. The use of the concrete analogy in steel design is supported but may result in overestimating the development length required 42

43 Simple Beam Flexural Test 2 15M Bar Beam 1 Set Up Flexural Capacity Achieved 43

44 Simple Beam Flexural Test 2 10M Bar Beam 2 Set Up Flexural Capacity Achieved 44

45 Simple Beam Test Results Beam 1 Beam 2 200mm X 300mm X 1500mm 200mm X 300mm X 1500mm 8 X10 X60 8X10X60 8 X10 X60 8X10X M (#5) deformed rebars 2 10M (#3) deformed rebars Three point loading system Three point loading system Failed at peak shear load of 78 kn Dfl Deflection at peak approximately 5.5mm (.22 ) Shear failure Failed at peak shear load of 60 kn Dfl Deflection at peak approximately 4.5mm (.17 ) Shear failure 45

46 46

47 Composite Wall Column Out of Plane Bending Wall Columns Forms Removed Composite Section View 47

48 Composite Wall Column Out of Plane Bending Open Stirrup Diagonal Stirrup 48

49 Composite Wall Column Out of Plane Bending Column 1 Deflection Dfl LVDTs and Cracks 49

50 Composite Wall Column Out of Plane Bending Column 2 Deflection Column Removed Via Forklift 50

51 Composite Wall Column Out of Plane Bending Results Column 1 Column 2 Open horizontal stirrup Diagonal Tie Tested indisplacementcontrol control Tested indisplacementcontrol control Load applied along entire face Load applied along entire face Maximum deflection exceeded Maximum deflection of 25mm 30mm (1.2 ) (1.0 ) Maximum load just under 60 Maximum load of 155 kn kn 51

52 Load vs Displacement for Column 1 with Horizontal Stirrups 52

53 Load vs. Displacement for Column 2 with Diagonal Stirrups 53

54 Conclusions: ThorTandy Tandy (Unisol Engineering) Bothcolumns met or exceeded the expectations of the researchers based upon the masonry analogy and the concrete analogy The data supports the use of either of these steel reinforcing approaches on single story SRE walls The diagonal stirrup in Column 2 resulted in a load capacity approx. 250% of the horizontal stirrup This approach could be used where shear loading is of greater concern 54

55 Future Research Exploration of the cement bond or mechanical bond on deformed steel reinforcing The effects of shear reinforcing on beam tests The effects of rigid foam on the shear capacities of composite SRE walls The bond strength of steel reinforcing in lower strength SRE A comprehensive analysis of the different types of insulations used in rammed earth walls The strength capacities of SRE mixes that utilize environmentally beneficial i pozzolans with a reduced cement content 55

56 Acknowledgments Hall, M. A. Assessing the moisture content dependent parameters of stabilized earth materials using the cyclic response admittancemethod method, 2008 Fix, Stuart & Richman, Russell Viability of Rammed Earth Building Construction in Cold Climates, 2009 Jaquin, Paul Website Photo Tandy, Thor Engineering Conclusions, R&D #1, BCIT NAREBA For test design and construction of the test specimens. The Cement Association of Canada for funding contributions Dr. Rishi Gupta (BCIT Instructor and Head of Dept.) who coordinated the testing protocol. Significantassistance assistance was provided on the laboratoryfloorby by Ken Zeleschuk and Iraj Manshadi. Bly Windstorm & NAREBA